The following invention relates to fasteners for coupling one or more devices which leak gas, and more specifically, to a fastener for coupling a cylinder head to an internal combustion engine.
A common design practice for internal combustion engines is to fasten the cylinder head to the engine block by means of bolts. This bolted joint also compresses a gasket for sealing various operating fluids including combustion gases. Under some conditions and over extended time intervals combustion gas seepage occurs across the gasket and into the closed annular cavity defined by the shank of the bolt and the through hole in the head. Water vapor and corrosive agents in this gas can collect in sufficient concentrations to cause significant corrosion on exposed metal surfaces. This situation is aggravated further if one end of the cavity is cooler than the other, resulting in a crude heat pipe. In this case, vapor concentration can become high enough at the cold end to actually condense on exposed surfaces. An example of this is a bolt located inside an air intake passage where passing air cools the head of the bolt relative to the threaded end. Such designs are prone to stress corrosion fatigue failure of the bolt at or near the point where the shank and the head of the bolt intersect.
Documents including various fastening and attachment concepts are shown in U.S. Pat. No. 80,435 to Way, issued Jul. 28, 1868; U.S. Pat. No. 131,408 to Peacock, issued Sep. 17, 1872; U.S. Pat. No. 2,320,398 to Zetterquist, issued Jun. 1, 1943; U.S. Pat. No. 3,209,640 to Waivers, issued Oct. 5, 1965; U.S. Pat. No. 3,408,812 to Stenger, issued Nov. 5, 1968; U.S. Pat. No. 4,302,941 to DuBell, issued Dec. 1, 1981; U.S. Pat. No. 4,597,258 to Harris, issued Jul. 1, 1986; U.S. Pat. No. 4,748,806 to Drobny, issued Jun. 7, 1988; U.S. Pat. No. 4,749,029 to Becker et al., issued Jun. 7, 1988; U.S. Pat. No. 4,749,298 to Bundt et al., issued Jun. 7, 1988; U.S. Pat. No. 4,820,097 to Maeda et al, issued Apr. 11, 1989; U.S. Pat. No. 4,944,151 to Hovnanian, issued Jul. 31, 1990; U.S. Pat. No. 5,080,542 to Sheahan, issued Jan. 14, 1992; U.S. Pat. No. 5,129,447 to Hamner, issued Jul. 14, 1992; U.S. Pat. No. 5,220,854 to Allart et al., issued Jun. 22, 1993; and European Patent No. 0 021 161 published Jan. 7, 1981.
The present inventions describes a novel and unobvious way to reduce corrosion of a fastener.
One embodiment of the present invention is a unique apparatus to fasten together two members. The apparatus includes means for establishing fluid communication from an area within one of the fastened members to an area external to both fastened members, the means for establishing fluid communication being part of the apparatus.
Another embodiment of the present invention includes a method for coupling two members together. The method includes coupling the members together, forming a chamber between the two members, and venting any gas within the chamber.
Yet another embodiment of the present invention includes coupling a cylinder head of an internal combustion engine to a second member with a fastener, and including means for venting gas which flows into a chamber defined between the fastener and the cylinder head.
These and other embodiments of the present invention will be described in the Description of the Preferred Embodiment, the claims, and the drawings to follow.